I do it all the time now, I can't remember if that fixed my issue or not but here is my export setup. The only difference between mine and John's is the version of .dwg being exported. Just recently I exported a 3GB truck to .dwg, it took a miniute but it worked.

If I remember correctly in the end for me it was a corrupt import file that I got from ford. Sorry I couldn't be more help. You might try to export to *.dxf which easily translates to *.dwg on the other side.